Ruthenium(II) complexes of Schiff base derived from cycloalkylamines as pre-catalysts for ROMP of norbornene and ATRP of methyl methacrylate

Ruthenium(II) complexes of Schiff base derived from cycloalkylamines (cycloalkyl = cyclopentyl (1a), cyclohexyl (1b), cycloheptyl (1c), and cyclooctyl) (1d) were synthesized: [RuCl(CyPen-Salen)(PPh3) 2] (2a), [RuCl(CyHex-Salen)(PPh3)(2)] (2b), [RuCl(CyHep-Salen)(PPh3)(2)] (2c), and [RuCl(CyOct-Salen)(PPh3) 2] (2d). The Schiff base-RuII complexes 2a-d were characterized by elemental analysis, FTIR, UV-Vis, 1H-, 13C and 31pNMR, and cyclic voltammetry. The complexes 2a-d were evaluated as catalytic precursors for ROMpof norbornene (NBE) and for ATRpof methyl methacrylate (MMA). The syntheses of polynorbornene (polyNBE) via ROMpwith complexes 2a-d as pre-catalysts were evaluated under different reaction conditions ([HCl]/[Ru], [EDA]/[Ru], [NBE]/[Ru], and temperature). The highest yields of polyNBE were obtained with [NBE]/[HCl]/[Ru] = 5000/25/1 M ratio in the presence of 5 mL of EDA for 60 min at 50 degrees C. MMA polymerization via ATRpwas conducted using the complexes 2a-d in the presence of ethyla- bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] = 1000/2/1 at 85 degrees C. The linear correlation of ln([MMA](0)/[MMA]) and time indicates that the concentration of radicals remains constant during the polymerization and that the ATRpof MMA mediated by 2a-d proceeds in a controlled manner. Molecular weights increased linearly with conversion, however, the experimental molecular weights were higher than the theoretical ones. (C) 2017 Elsevier B.V. All rights reserved.